Technical Field
This disclosure relates to medical instrument guidance systems and methods, and more particularly to needle guidance using smart needles and images fused to provide greater visualization of the needle guidance.
Description of the Related Art
The past decade has seen an increase in use of ultrasound in epidural interventions, with predictions that it would soon be part of the standard of clinical care. However, one challenge for ultrasound guided epidurals is the difficulty in seeing the needle without crossing into the spine. Physicians primarily rely on the loss of resistance to detect this passage, a highly subjective maneuver, possibly leading to complications. Spine-related pain has been a common cause of morbidity. Back pain along with the substantial medical costs of diagnosis and treatment has imposed a burden and productivity loss. An epidural injection is one of many methods being considered to relieve pain, along with physical therapy, oral medications and surgery if a patient is not responding to conservative treatments. An epidural injection is delivered into the epidural space of the spine to provide temporary or prolonged relief from pain or inflammation.
Three layers of tissue cover the spinal cord. An epidural space is the area of space between an outermost tissue layer (dura) of the spinal cord and an inside surface of bone and supporting ligaments in which it is contained. The epidural space runs the length of the spine. The epidural space contains fat tissue along with blood vessels and nerve roots. An epidural injection may be performed to alleviate pain caused by a herniated or bulging disk, spinal stenosis, post-operative “failed back” surgery syndromes (chronic back or leg pain after spinal surgery), or other injuries to spinal nerves, vertebrae and surrounding tissues.
Epidural anesthesia is also administered for births and for many surgical procedures. Complications of administering epidural anesthesia arise due to incorrect needle positioning during the injection but rarely cause any permanent damage to the patient. However, the complications could be reasonably disconcerting and could persist for several days. During epidural anesthesia, the placement of the needle is important to effectively administer pain relief and avoid nerve damage. However, accurate epidural needle insertion is difficult to learn and typically relies on the expertise of an anesthesiologist to detect a loss of resistance on the needle plunger to determine placement.
Portable ultrasound is increasingly used to help needle positioning for epidural and other injections or spinal taps and other biopsies, especially in the presence of challenging anatomies (high body mass index (BMI), scoliosis, etc.). However, ultrasound does not visualize the needle tip well especially for procedures where needle insertion is very steep. Also, tissues (e.g., ligamentum flavum) may be difficult to see even with ultrasound guidance due to the challenging environment for ultrasound (e.g., the presence of bones).
Needle visualization such as electromagnetic tracking has been demonstrated to highlight the needle tip on an ultrasound image, and products are available for anesthesia and biopsy guidance. However, the high expense of these needles and the cumbersome setup time has attenuated the adoption of this technology. Other ways to improve needle visualization include the addition of another imaging modality to the workflow such as X-ray or even computed tomography (CT), but this makes the procedure significantly more cumbersome.